What makes Emperor's Return by Celtic Frost notable?

'Emperor's Return' is significant for its influence on the extreme metal genre, showcasing Celtic Frost's avant-garde approach. The EP helped pioneer the sound that would be pivotal for future bands in black and death metal scenes, cementing the band's reputation as innovators. Released in 1985, 'Emperor's Return' is Celtic Frost's follow-up to their debut album, 'Morbid Tales'. At this point in their career, the band was solidifying their unique sound that blended elements of black and death metal, while pushing the boundaries of extreme music.